The present invention generally relates to an energy storage system, and more particularly, to an energy storage module to be incorporated into a hybrid electric motor vehicle to store high voltage energy.
Vehicles incorporating electric motors require high voltage energy storage systems in order to properly power the motor. High voltage energy storage often encompasses multiple battery cells which are electrically connected together in series. Storage cells, when charging or discharging generate heat due to chemical reactions within the cells, as heat generation is a byproduct of electricity generation. When multiple battery cells are contained in close proximity, as in an array, the heat generated in each cell can become multiplicative throughout the system and can cause problems such as cell thermal runaway which can destroy the storage system. Additionally, for optimal energy efficiency, uniform temperature of the battery cells is preferred. Thus it is advantageous for such storage systems to include a cooling system to cool the battery cells.
Commonly, hybrid and electric energy storage cooling systems use an open system design which allows external air to reach the battery cells. Often these systems use convective heat transfer to reduce the temperatures of the batteries by passing air over the batteries which circulates from an external intake to an external exhaust. These systems are susceptible to problems caused by salt, dust, and other debris that can reach the battery cells by entering the air intake. Open cooling systems do not prevent salt fog or other corrosive materials from reaching the battery cells, even when a filter is used. Salt fog and foreign particles can cause corrosion and unwanted electrical leakage current paths or short circuits to exist in the storage system. Correspondingly, the system can cause a reduced battery cell life compared to a closed system. Open cooling systems can necessitate installation and use of drain plugs to remove foreign substances from the battery enclosure. Additionally, open cooling system designs add volume to the battery array system which causes problems with space-efficient original designs or hybrid retrofit applications.
The above problems as well as other problems with open cooling systems demonstrate a need in the field for alternative cooling systems for battery cell arrays such as various types of closed cooling systems.